I found a GOOD solution now through wereldwijdwifi.nl
Maybe not the cheapest per GB, but you ONLY pay when you use it, and the GBs you don't use up, stay valid for a year. No more worries about not using up the monthly GBs you've paid for.
And no more obscure messages or warnings in Italian either.

And no, I do not have an interest in their business, am just SO relieved!!

After purchasing your own MiFi or SIM card can be purchased at any time data bundles. You buy credit data through our site which is valid for one year. On our site you can see exactly how much data you have left and how long it is valid. If you have some data have on your account and you buy a new data bundle, then everything is again valid for one year.

When purchasing your Mi-Fi (€ 79.95) or EU sim (€ 24.95) you get all free 1 GB of data. If you need more, you can easily purchase additional credit data at any time. So go. Your logs in on the site with your customer number and then pay safely using iDEAL, credit card or PayPal. You can choose from the following data bundles:

the SIM includes some potential expensive destination like Switzerland, so the rates are OK for today.
After june ths year you will be able to use cheaper SIM as then all cards must include EU roaming (or block roaming in general)

That varies. Norway is EEA and always included in EU roaming. The EEA adopts EU rules and consists of Iceland, Norway and Liechtenstein.

Switzerland is different. Some providers include it, others don't as it's not mandatory. It actually varies with the same provider according to country:
For instance Vodafone in the UK includes Switzerland, Turkey, and Albania on a voluntary basis, Vodafone Netherlands includes Switzerland too, but Vodafone Germany which is neighboring Switzerland don't. All Italian and Austrian providers exclude Switzerland too. Vodafone Spain has actually included the US !!! to their EU Roam like home zone.

So this is what we can expect when the UK will eventually leave the EU/EEA. It will be treated like Switzerland and this is very variable. In Germany operators have changed their T&Cs for the case one member leaves the EU. So many will put it to their out-of-Europe-cat.

The rush for Vodafone NL as a roaming SIM is partly because of our recommendation in the prepaid-data-Wiki. But we will take it off in June as there will be many more choices with "roam like (at) home" implemented. In a few days I will give here an update about the implementation.

I'm collecting the new roaming rates from EU providers. The "roam like at home" principle with roaming rates equal to domestic rates will face some restrictions. Not according to where you roam, but where the SIM card is issued. As it looks like we have 3 groups of countries in the EU/EEA:
1.) those that adopt Roam like at home without restrictions or any FUP like UK, Germany, Netherlands, Spain, Czech Rep.....
2.) those that restrict large data packages from which only a part is given out at domestic rates like Italy, Ireland, France, Austria, Sweden ....
3.) those that opt-out completely and still will surcharge roaming under the derogation FUP like Estonia, Latvia, Lithuania and Poland

It looks like that Roam like at home will not be available to about 100 million users in the countries of 3.) But we need to wait a little bit more to see more roaming plans coming in for this summer and how the national regulators decide about the applications for the derogation.